Flame retardant resinous compositions and process

ABSTRACT

Disclosed is a flame-retardant composition comprising (i) 40-66 wt. % alkenyl aromatic resin, (ii) 9-33 wt. % ammonium polyphosphate and (iii) 14-40 wt. % cellulosic material, wherein all weights are based on the total weight of the composition and wherein ammonium polyphosphate and cellulosic material are present in a weight % ratio effective to provide molded articles exhibiting at least V-1 flame rating as determined according to the UL-94 protocol. A process to prepare the composition and articles comprising a composition of the invention and/or made by the process of the invention described herein are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of applicationSer. No. 12/022,420, filed Jan. 30, 2008, which is incorporated hereinby reference.

BACKGROUND

The present invention relates to flame retardant resinous compositionscomprising an alkenyl aromatic resin and a cellulosic material.

Flame retardant resinous compositions comprising an alkenyl aromaticresin, such as a styrenic resin, typically comprise a halogen-containingflame retardant additive. In order to minimize environmental, health andsafety (EHS) issues, there is a great market need to develop flameretardant alkenyl aromatic resin compositions containing non-halogenflame retardant additives. Such compositions are known as eco-friendlyflame retardant compositions. Typically, it has not been possible todevelop flame retardant alkenyl aromatic resin compositions withouthalogen-containing additives with needed flammability rating whilemaintaining good mechanical properties and desirable processingcharacteristics. Hence, there is a need for eco-friendly flame retardantalkenyl aromatic resin compositions with suitable flame retardantproperties which compositions also possess an attractive balance ofmechanical properties.

BRIEF DESCRIPTION

The present inventors have discovered eco-friendly flame retardantalkenyl aromatic resin compositions which have flame retardantproperties in combination with an attractive balance of mechanicalproperties. Articles made from the compositions of the present inventionoften exhibit V-1 flame rating or better as determined according to theUL-94 protocol. The articles are useful in applications requiring flameresistance, and particularly in applications requiring halogen-free(eco-friendly) compositions for flame resistance. This inventionprovides a unique solution for eco-friendly flame retardant polymerproducts using cost effective additives.

In one embodiment the present invention comprises a resinous,flame-retardant composition comprising (i) 40-66 wt. % alkenyl aromaticresin, (ii) 9-33 wt. % ammonium polyphosphate and (iii) 14-40 wt. %cellulosic material, wherein all weights are based on the total weightof the composition and wherein ammonium polyphosphate and cellulosicmaterial are present in a weight % ratio effective to provide moldedarticles exhibiting at least V-1 flame rating as determined according tothe UL-94 protocol.

In another embodiment the present invention comprises a resinous,flame-retardant composition comprising (i) 40-66 wt. % alkenyl aromaticresin, (ii) 9-33 wt. % ammonium polyphosphate and (iii) 14-40 wt. %cellulosic material, wherein ammonium polyphosphate and cellulosicmaterial are present in a weight % ratio in a range of 1:2 to 2:1effective to provide molded articles exhibiting at least V-1 flamerating as determined according to the UL-94 protocol, and wherein thecomposition is prepared by an extrusion process wherein all or a portionof the ammonium polyphosphate is fed to the extruder down-stream fromthe alkenyl aromatic resin and the cellulosic material.

In still another embodiment the present invention comprises an extrusionprocess for preparing a resinous, flame-retardant composition comprising(i) 40-66 wt. % alkenyl aromatic resin, (ii) 9-33 wt. % ammoniumpolyphosphate and (iii) 14-40 wt. % cellulosic material, whereinammonium polyphosphate and cellulosic material are present in a weight %ratio in a range of 1:2 to 2:1 effective to provide molded articlesexhibiting at least V-1 flame rating as determined according to theUL-94 protocol, which process comprises the step of adding at least aportion of the ammonium polyphosphate to the extruder down-stream fromthe ABS and the cellulosic material. Articles comprising a compositionof the invention and/or made by the process described are alsodisclosed. Various other features, aspects, and advantages of thepresent invention will become more apparent with reference to thefollowing description and appended claims.

DETAILED DESCRIPTION

In the following specification and the claims which follow, referencewill be made to a number of terms which shall be defined to have thefollowing meanings. The singular forms “a”, “an” and “the” includeplural referents unless the context clearly dictates otherwise. Theterminology “monoethylenically unsaturated” means having a single siteof ethylenic unsaturation per molecule. The terminology“polyethylenically unsaturated” means having two or more sites ofethylenic unsaturation per molecule. The terminology “(meth)acrylate”refers collectively to acrylate and methacrylate; for example, the term“(meth)acrylate monomers” refers collectively to acrylate monomers andmethacrylate monomers. The term “(meth)acrylamide” refers collectivelyto acrylamides and methacrylamides.

The term “alkyl” as used in the various embodiments of the presentinvention is intended to designate linear alkyl, branched alkyl,aralkyl, cycloalkyl, bicycloalkyl, tricycloalkyl and polycycloalkylradicals containing carbon and hydrogen atoms, and optionally containingatoms in addition to carbon and hydrogen, for example atoms selectedfrom Groups 15, 16 and 17 of the Periodic Table. Alkyl groups may besaturated or unsaturated, and may comprise, for example, alkenyl, vinylor allyl. The term “alkyl” also encompasses that alkyl portion ofalkoxide groups. In various embodiments normal and branched alkylradicals are those containing from 1 to about 32 carbon atoms, andinclude as illustrative non-limiting examples C₁-C₃₂ alkyl (optionallysubstituted with one or more groups selected from C₁-C₃₂ alkyl, C₃-C₁₅cycloalkyl or aryl); and C₃-C₁₅ cycloalkyl optionally substituted withone or more groups selected from C₁-C₃₂ alkyl. Some particularillustrative examples comprise methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tertiary-butyl, pentyl, neopentyl, hexyl, heptyl,octyl, nonyl, decyl, undecyl and dodecyl. Some illustrative non-limitingexamples of cycloalkyl and bicycloalkyl radicals include cyclobutyl,cyclopentyl, cyclohexyl, methylcyclohexyl, cycloheptyl, bicycloheptyland adamantyl. In various embodiments aralkyl radicals are thosecontaining from 7 to about 14 carbon atoms; these include, but are notlimited to, benzyl, phenylbutyl, phenylpropyl, and phenylethyl. The term“aryl” as used in the various embodiments of the present invention isintended to designate substituted or unsubstituted aryl radicalscontaining from 6 to 20 ring carbon atoms. Some illustrativenon-limiting examples of these aryl radicals include C₆-C₂₀ aryloptionally substituted with one or more groups selected from C₁-C₃₂alkyl, C₃-C₁₅ cycloalkyl, aryl, and functional groups comprising atomsselected from Groups 15, 16 and 17 of the Periodic Table. Someparticular illustrative examples of aryl radicals comprise substitutedor unsubstituted phenyl, biphenyl, tolyl, naphthyl and binaphthyl.

Compositions in embodiments of the present invention comprise at leastone alkenyl aromatic resin. There is no particular limitation on thealkenyl aromatic resin which in some embodiments may comprise one ormore homopolymers, copolymers, core-shell resins or rubber-modifiedresins. In some particular embodiments alkenyl aromatic resins compriseat least one polymeric material with structural units derived fromstyrene. In other particular embodiments alkenyl aromatic resins areselected from the group consisting of polystyrene, expandablepolystyrene, acrylonitrile-butadiene-styrene copolymer (ABS),rubber-modified polystyrene, high-impact polystyrene (HIPS),styrene-acrylonitrile copolymer (SAN), alkylmethacrylate-styrene-acrylonitrile copolymer, methylmethacrylate-styrene-acrylonitrile copolymer, styrene-butadienecopolymer, styrene-maleic anhydride copolymer, styrene-methyl acrylatecopolymer, styrene-methyl methacrylate copolymer,alpha-methylstyrene/acrylonitrile copolymer,alpha-methylstyrene/styrene/acrylonitrile copolymer, polychlorostyrene,polyvinyltoluene, and the like and mixtures thereof.

In some embodiments compositions of the present invention comprise atleast one rubber modified thermoplastic resin comprising a discontinuouselastomeric phase dispersed in a rigid thermoplastic phase, wherein atleast a portion of the rigid thermoplastic phase is grafted to theelastomeric phase. The rubber modified thermoplastic resin employs atleast one rubber substrate for grafting. The rubber substrate comprisesthe elastomeric phase of the composition. There is no particularlimitation on the rubber substrate provided it is susceptible tografting by at least a portion of a graftable monomer. In someembodiments suitable rubber substrates comprise butyl acrylate rubber,dimethyl siloxane/butyl acrylate rubber, or silicone/butyl acrylatecomposite rubber; polyolefin rubbers such as ethylene-propylene rubberor ethylene-propylene-diene (EPDM) rubber; diene-derived rubbers; orsilicone rubber polymers such as polymethylsiloxane rubber. The rubbersubstrate typically has a glass transition temperature, Tg, in oneembodiment less than or equal to 25° C., in another embodiment belowabout 0° C., in another embodiment below about minus 20° C., and instill another embodiment below about minus 30° C. As referred to herein,the Tg of a polymer is the T value of polymer as measured bydifferential scanning calorimetry (DSC; heating rate 20° C./minute, withthe Tg value being determined at the inflection point).

In one embodiment the rubber substrate comprises a polymer havingstructural units derived from one or more unsaturated monomers selectedfrom conjugated diene monomers and non-conjugated diene monomers.Suitable conjugated diene monomers include, but are not limited to,1,3-butadiene, isoprene, 1,3-heptadiene, methyl-1,3-pentadiene,2,3-dimethylbutadiene, 2-ethyl-1,3-pentadiene, 1,3-hexadiene,2,4-hexadiene, dichlorobutadiene, bromobutadiene and dibromobutadiene aswell as mixtures of conjugated diene monomers. In a particularembodiment the conjugated diene monomer is 1,3-butadiene. Suitablenon-conjugated diene monomers include, but are not limited to,ethylidene norbornene, dicyclopentadiene, hexadiene and phenylnorbornene.

In some embodiments the rubber substrate may optionally comprisestructural units derived from minor amounts of other unsaturatedmonomers, for example up to about 30 percent by weight (“wt. %”) ofstructural units derived from one or more monomers selected from(C₂-C₈)olefin monomers, alkenyl aromatic monomers and monoethylenicallyunsaturated nitrile monomers. As used herein, the term “(C₂-C₈)olefinmonomers” means a compound having from 2 to 8 carbon atoms per moleculeand having a single site of ethylenic unsaturation per molecule.Suitable (C₂-C₈)olefin monomers include, e.g., ethylene, propene,1-butene, 1-pentene, heptene. In other particular embodiments the rubbersubstrate may optionally include up to about 25 wt. % of structuralunits derived from one or more monomers selected from (meth)acrylatemonomers, alkenyl aromatic monomers and monoethylenically unsaturatednitrile monomers. Suitable copolymerizable (meth)acrylate monomersinclude, but are not limited to, C₁-C₁₂ aryl or haloaryl substitutedacrylate, C₁-C₁₂ aryl or haloaryl substituted methacrylate, or mixturesthereof, monoethylenically unsaturated carboxylic acids, such as, forexample, acrylic acid, methacrylic acid and itaconic acid;glycidyl(meth)acrylate, hydroxy alkyl(meth)acrylate,hydroxy(C₁-C₁₂)alkyl(meth)acrylate, such as, for example, hydroxyethylmethacrylate; (C₄-C₁₂)cycloalkyl(meth)acrylate monomers, such as, forexample, cyclohexyl methacrylate; (meth)acrylamide monomers, such as,for example, acrylamide, methacrylamide and N-substituted-acrylamide orN-substituted-methacrylamides; maleimide monomers, such as, for example,maleimide, N-alkyl maleimides, N-aryl maleimides, N-phenyl maleimide,and haloaryl substituted maleimides; maleic anhydride; methyl vinylether, ethyl vinyl ether, and vinyl esters, such as, for example, vinylacetate and vinyl propionate. Suitable alkenyl aromatic monomersinclude, but are not limited to, vinyl aromatic monomers, such as, forexample, styrene and substituted styrenes having one or more alkyl,alkoxy, hydroxy or halo substituent groups attached to the aromaticring, including, but not limited to, alpha-methyl styrene, p-methylstyrene, 3,5-diethylstyrene, 4-n-propylstyrene, 4-isopropylstyrene,vinyl toluene, alpha-methyl vinyl toluene, vinyl xylene, trimethylstyrene, butyl styrene, t-butyl styrene, chlorostyrene,alpha-chlorostyrene, dichlorostyrene, tetrachlorostyrene, bromostyrene,alpha-bromostyrene, dibromostyrene, p-hydroxystyrene, p-acetoxystyrene,methoxystyrene and vinyl-substituted condensed aromatic ring structures,such as, for example, vinyl naphthalene, vinyl anthracene, as well asmixtures of vinyl aromatic monomers and monoethylenically unsaturatednitrile monomers such as, for example, acrylonitrile, ethacrylonitrile,methacrylonitrile, alpha-bromoacrylonitrile and alpha-chloroacrylonitrile. Substituted styrenes with mixtures of substituents on thearomatic ring are also suitable. As used herein, the term“monoethylenically unsaturated nitrile monomer” means an acycliccompound that includes a single nitrile group and a single site ofethylenic unsaturation per molecule and includes, but is not limited to,acrylonitrile, methacrylonitrile, alpha-chloro acrylonitrile, and thelike.

In a particular embodiment the elastomeric phase comprises from 60 to100 wt. % repeating units derived from one or more conjugated dienemonomers and from 0 to 40 wt. % repeating units derived from one or moremonomers selected from alkenyl aromatic monomers and monoethylenicallyunsaturated nitrile monomers, such as, for example, a styrene-butadienecopolymer, an acrylonitrile-butadiene copolymer or astyrene-butadiene-acrylonitrile copolymer. In another particularembodiment the elastomeric phase comprises from 70 to 90 wt. % repeatingunits derived from one or more conjugated diene monomers and from 30 to10 wt. % repeating units derived from one or more monomers selected fromalkenyl aromatic monomers.

The rubber substrate may be present in the rubber modified thermoplasticresin in one embodiment at a level of from about 5 wt. % to about 80 wt.%, based on the weight of the rubber modified thermoplastic resin. Inone particular embodiment the rubber substrate may be present in therubber modified thermoplastic resin at a level of from about 10 wt. % toabout 25 wt. %, based on the weight of the rubber modified thermoplasticresin. In another particular embodiment the rubber substrate may bepresent in the rubber modified thermoplastic resin at a level of fromabout 55 wt. % to about 80 wt. %, based on the weight of the rubbermodified thermoplastic resin.

There is no particular limitation on the particle size distribution ofthe rubber substrate (sometimes referred to hereinafter as initialrubber substrate to distinguish it from the rubber substrate followinggrafting). In some embodiments the initial rubber substrate may possessa broad, essentially monomodal, particle size distribution withparticles ranging in size from about 50 nanometers (nm) to about 1000nm, and more particularly with particles ranging in size from about 200nm to about 500 nm. In other embodiments the mean particle size of theinitial rubber substrate may be less than about 100 nm. In still otherembodiments the mean particle size of the initial rubber substrate maybe in a range of between about 80 nm and about 400 nm. In otherembodiments the mean particle size of the initial rubber substrate maybe greater than about 400 nm. In still other embodiments the meanparticle size of the initial rubber substrate may be in a range ofbetween about 400 nm and about 750 nm. In still other embodiments theinitial rubber substrate comprises particles which are a mixture ofparticle sizes with at least two mean particle size distributions. In aparticular embodiment the initial rubber substrate comprises a mixtureof particle sizes with each mean particle size distribution in a rangeof between about 80 nm and about 750 nm. In another particularembodiment the initial rubber substrate comprises a mixture of particlesizes, one with a mean particle size distribution in a range of betweenabout 80 nm and about 400 nm; and one with a broad and essentiallymonomodal mean particle size distribution.

The rubber substrate may be made according to known methods, such as,but not limited to, a bulk, solution, or emulsion process. In onenon-limiting embodiment the rubber substrate is made by aqueous emulsionpolymerization in the presence of a free radical initiator, e.g., anazonitrile initiator, an organic peroxide initiator, a persulfateinitiator or a redox initiator system, and, optionally, in the presenceof a chain transfer agent, e.g., an alkyl mercaptan, to form particlesof rubber substrate.

The rigid thermoplastic resin phase of the rubber modified thermoplasticresin comprises one or more thermoplastic polymers. In one embodiment ofthe present invention monomers are polymerized in the presence of therubber substrate to thereby form the rigid thermoplastic phase, at leasta portion of which is chemically grafted to the elastomeric phase. Theportion of the rigid thermoplastic phase chemically grafted to rubbersubstrate is sometimes referred to hereinafter as grafted copolymer. Insome embodiments two or more different rubber substrates, eachpossessing a different mean particle size, may be separately employed ina polymerization reaction to prepare the rigid thermoplastic phase, andthen the products blended together to make the rubber modifiedthermoplastic resin. In illustrative embodiments wherein such productseach possessing a different mean particle size of initial rubbersubstrate are blended together, then the ratios of said substrates maybe in a range of about 90:10 to about 10:90, or in a range of about80:20 to about 20:80, or in a range of about 70:30 to about 30:70. Insome embodiments an initial rubber substrate with smaller particle sizeis the major component in such a blend containing more than one particlesize of initial rubber substrate.

The rigid thermoplastic phase comprises a thermoplastic polymer orcopolymer that exhibits a glass transition temperature (Tg) in oneembodiment of greater than about 25° C., in another embodiment ofgreater than or equal to 90° C., and in still another embodiment ofgreater than or equal to 100° C. In a particular embodiment the rigidthermoplastic phase comprises a polymer having structural units derivedfrom one or more monomers selected from the group consisting of alkenylaromatic monomers and monoethylenically unsaturated nitrile monomers.Suitable alkenyl aromatic monomers and monoethylenically unsaturatednitrile monomers include those set forth hereinabove in the descriptionof the rubber substrate. In addition, the rigid thermoplastic resinphase may, provided that the Tg limitation for the phase is satisfied,optionally include up to about 10 wt. % of third repeating units derivedfrom one or more other copolymerizable monomers.

The rigid thermoplastic phase typically comprises one or more alkenylaromatic polymers. Suitable alkenyl aromatic polymers comprise at leastabout 20 wt. % structural units derived from one or more alkenylaromatic monomers. In one embodiment the rigid thermoplastic phasecomprises an alkenyl aromatic polymer having structural units derivedfrom one or more alkenyl aromatic monomers and from one or moremonoethylenically unsaturated nitrile monomers. Examples of such alkenylaromatic polymers include, but are not limited to, styrene/acrylonitrilecopolymers, alpha-methylstyrene/acrylonitrile copolymers, oralpha-methylstyrene/styrene/acrylonitrile copolymers. These copolymersmay be used for the rigid thermoplastic phase either individually or asmixtures.

When structural units in copolymers are derived from one or moremonoethylenically unsaturated nitrile monomers, then the amount ofnitrile monomer added to form the copolymer comprising the graftedcopolymer and the rigid thermoplastic phase may be in one embodiment ina range of between about 5 wt. % and about 40 wt. %, in anotherembodiment in a range of between about 5 wt. % and about 30 wt. %, inanother embodiment in a range of between about 10 wt. % and about 30 wt.%, and in yet another embodiment in a range of between about 15 wt. %and about 30 wt. %, based on the total weight of monomers added to formthe copolymer comprising the grafted copolymer and the rigidthermoplastic phase.

The rigid thermoplastic resin phase of the rubber modified thermoplasticresin may, provided that the Tg limitation for the phase is satisfied,optionally include up to about 10 wt. % of repeating units derived fromone or more other copolymerizable monomers such as, e.g.,monoethylenically unsaturated carboxylic acids such as, e.g., acrylicacid, methacrylic acid, and itaconic acid; hydroxy(C₁-C₁₂)alkyl(meth)acrylate monomers such as, e.g., hydroxyethyl methacrylate;(C₄-C₁₂)cycloalkyl (meth)acrylate monomers such as e.g., cyclohexylmethacrylate; (meth)acrylamide monomers such as e.g., acrylamide andmethacrylamide; maleimide monomers such as, e.g., N-alkyl maleimides,N-aryl maleimides, maleic anhydride, vinyl esters such as, e.g., vinylacetate and vinyl propionate. As used herein, the term“(C₄-C₁₂)cycloalkyl” means a cyclic alkyl substituent group having from4 to 12 carbon atoms per group.

The amount of grafting that takes place between the rubber substrate andmonomers comprising the rigid thermoplastic phase varies with therelative amount and composition of the rubber substrate. In oneembodiment, greater than about 10 wt. % of the rigid thermoplastic phaseis chemically grafted to the rubber substrate, based on the total amountof rigid thermoplastic phase in the composition. In another embodiment,greater than about 15 wt. % of the rigid thermoplastic phase ischemically grafted to the rubber substrate, based on the total amount ofrigid thermoplastic phase in the composition. In still anotherembodiment, greater than about 20 wt. % of the rigid thermoplastic phaseis chemically grafted to the rubber substrate, based on the total amountof rigid thermoplastic phase in the composition. In particularembodiments the amount of rigid thermoplastic phase chemically graftedto the rubber substrate may be in a range of between about 5 wt. % andabout 90 wt. %; between about 10 wt. % and about 90 wt. %; between about15 wt. % and about 85 wt. %; between about 15 wt. % and about 50 wt. %;or between about 20 wt. % and about 50 wt. %, based on the total amountof rigid thermoplastic phase in the composition. In yet otherembodiments, about 40 wt. % to 90 wt. % of the rigid thermoplastic phaseis free, that is, non-grafted.

The rigid thermoplastic phase polymer may be made according to knownprocesses, for example, mass polymerization, emulsion polymerization,suspension polymerization or combinations thereof, wherein at least aportion of the rigid thermoplastic phase is chemically bonded, i.e.,“grafted” to the rubber substrate via reaction with unsaturated sitespresent in the rubber substrate in the case of the rigid thermoplasticphase. The grafting reaction may be performed in a batch, continuous orsemi-continuous process.

In particular embodiments compositions of the invention comprise arubber modified thermoplastic resin which is an ABS resin. IllustrativeABS resins suitable for use in compositions of the present inventioncomprise those available from SABIC Innovative Plastics™ under thetradename CYCLOLAC®. In some particular embodiments compositions of theinvention comprise 5-50 wt. % rubber derived from at least one alkenylaromatic resin such as ABS, the wt. % value being based on the weight ofthe entire composition, wherein the term “rubber” refers to the rubbersubstrate in ABS. In still other particular embodiments compositions ofthe invention comprise 5-35 wt. % rubber derived from at least onealkenyl aromatic resin such as ABS and based on the weight of the entirecomposition. In still other particular embodiments compositions of theinvention comprise 5-30 wt. % rubber derived from at least one alkenylaromatic resin such as ABS and based on the weight of the entirecomposition. In yet other particular embodiments compositions of theinvention comprise less than 30 wt. % rubber derived from at least onealkenyl aromatic resin such as ABS and based on the weight of the entirecomposition. The rubber content may be varied by employing a singlealkenyl aromatic resin with desired rubber content or by employing twoor more alkenyl aromatic resins each with different rubber content. Insome embodiments compositions of the invention comprise 40-70 wt. %alkenyl aromatic resin and in other embodiments 40-66 wt. % alkenylaromatic resin based on the total weight of the composition

Compositions in embodiments of the invention also comprise at least oneadditive comprising cellulose, which additive is sometimes referred toherein after as cellulosic material. In various embodiments thecellulosic material comprises or is derived from cellulosic fiber, woodfiber, seed husks, ground rice hulls, newspaper, kenaf, coconut shell,or like materials. In some specific embodiments the cellulosic materialmay be wood fiber, which is available in different forms. In otherillustrative examples cellulosic material comprises or is derived fromsawdust, alfalfa, wheat pulp, wood chips, wood particles, ground wood,wood flour, wood flakes, wood veneers, wood laminates, paper, cardboard,straw, cotton, peanut shells, bagass, plant fibers, bamboo fiber, palmfiber, or like materials. Those skilled in the art should recognize thatthe cellulosic material of the present invention may be any suitablecombination of different types of cellulosic material. In someparticular embodiments the cellulosic material is selected fromcellulosic fibers and wood flour.

Compositions in embodiments of the invention also comprise at least oneammonium polyphosphate. Ammonium polyphosphates are known materials andmay be prepared, for example, as exemplified in U.S. Pat. Nos. 3,423,343and 3,513,114. In some illustrative embodiments the ammoniumpolyphosphates have the general formula (NH₄)_(n)H₂P_(n)O_(3n+1),wherein n is 1 or more, or (NH₄PO₃)_(n) wherein n represents an integerequal to or greater than 2. Illustrative examples of commerciallyavailable ammonium polyphosphates comprise EXOLIT® ammoniumpolyphosphate produced and sold by Clariant, PHOS-CHECK® ammoniumpolyphosphate available from ICL Performance Products LP and FR CROS®ammonium polyphosphate available from Budenheim Iberica Comercial S.A.In one embodiment compositions of the invention comprise at least one“crystal phase II” ammonium polyphosphate which may be cross-linkedand/or branched. Crystal phase II ammonium polyphosphates are known inthe art. They are high molecular weight ammonium polyphosphates, andexhibit high thermal stability (for example, decomposition starting atabout 300° C.) and low water solubility. An illustrative example of acrystal phase II ammonium polyphosphate is EXOLIT® AP 423 available fromClariant. Coated ammonium polyphosphate may also be employed incompositions of the invention in some embodiments. Illustrative examplesof coated ammonium polyphosphates comprise melamine-coated ormelamine-formaldehyde-coated or surface-reacted melamine-coated ammoniumpolyphosphate. One illustrative coated ammonium polyphosphate is FRCROS® C40 available from Budenheim Iberica Comercial S.A.

In various embodiments of the invention ammonium polyphosphate andcellulosic material may be present together in compositions of theinvention in total amount by weight effective to provide articlesexhibiting at least V-1 flame rating or better as determined accordingto the UL-94 protocol. In particular embodiments ammonium polyphosphatemay be present in compositions of the invention in an amount in a rangeof between about 5 wt. % and about 35 wt. %, or in an amount in a rangeof between about 7 wt. % and about 33 wt. %, or in an amount in a rangeof between about 9 wt. % and about 33 wt. %, or in an amount in a rangeof between about 12 wt. % and about 33 wt. %, based on the weight of theentire composition. In particular embodiments cellulosic material may bepresent in compositions of the invention in an amount in a range ofbetween about 5 wt. % and about 45 wt. %, or in an amount in a range ofbetween about 10 wt. % and about 40 wt. %, or in an amount in a range ofbetween about 14 wt. % and about 40 wt. %, based on the weight of theentire composition. In other particular embodiments of the inventionammonium polyphosphate and cellulosic material may be present in aweight % ratio effective to provide articles exhibiting V-0 or V-1 orV-2 flame rating as determined according to the UL-94 protocol. In otherparticular embodiments of the invention ammonium polyphosphate andcellulosic material may be present in a weight % ratio in a range of1:10 to 10:1, often 1:8 to 8:1, more often 1:5 to 5:1, still more often1:3 to 3:1 and still more often 1:2 to 2:1.

Compositions of the present invention may also optionally compriseadditives known in the art including, but not limited to, stabilizers,such as color stabilizers, heat stabilizers, light stabilizers,antioxidants, UV screeners, and UV absorbers; adjunct flame retardants,anti-drip agents, lubricants, flow promoters or other processing aids;plasticizers, antistatic agents, mold release agents, impact modifiers,fillers, or colorants such as dyes or pigments which may be organic,inorganic or organometallic; visual effects additives and likeadditives. Illustrative additives include, but are not limited to,silica, silicates, zeolites, titanium dioxide, stone powder, glassfibers or spheres, carbon fibers, carbon black, graphite, calciumcarbonate, talc, lithopone, zinc oxide, zirconium silicate, iron oxides,diatomaceous earth, calcium carbonate, magnesium oxide, chromic oxide,zirconium oxide, aluminum oxide, crushed quartz, clay, calcined clay,talc, kaolin, asbestos, cellulose, wood flour, cork, cotton or synthetictextile fibers, especially reinforcing fillers such as glass fibers,carbon fibers, metal fibers, and metal flakes, including, but notlimited to aluminum flakes. Compositions of the invention do not containcornstarch or a metal stearate such as zinc stearate. Often more thanone additive is included in compositions of the invention, and in someembodiments more than one additive of one type is included.

In some particular embodiments compositions of the invention optionallycomprise at least one organophosphorus compound as an adjunct flameretardant. Suitable organophosphorus flame retardant compounds are knownin the art and include, but are not limited to, monophosphate esterssuch as triaryl phosphates, triphenyl phosphate, tricresyl phosphate,tritolyl phosphate, diphenylcresyl phosphate, phenyl bisdodecylphosphate, and ethyl diphenyl phosphate, as well as diphosphate estersand oligomeric phosphates such as, for example, aryl diphosphates,resorcinol diphosphate, bisphenol A diphosphate, diphenyl hydrogenphosphate, and 2-ethylhexyl hydrogen phosphate. Suitable oligomericphosphate compounds are set forth for example in U.S. Pat. No.5,672,645. An adjunct flame retardant, when present, is typicallypresent in an amount of about 4-16 wt. % and particularly 5-15 wt. %based on the weight of the entire composition.

Compositions of the invention and articles made therefrom may beprepared by known thermoplastic processing techniques. Knownthermoplastic processing techniques which may be used include, but arenot limited to, batch mixing, extrusion, calendering, kneading, profileextrusion, sheet extrusion, pipe extrusion, coextrusion, molding,extrusion blow molding, thermoforming, injection molding, co-injectionmolding, rotomolding, compression molding, and like processes andcombinations of such processes. In a particular embodiment compositionsare prepared by an extrusion process. In a particular embodimentarticles are prepared from compositions of the invention by an injectionmolding process. The invention further contemplates additionalfabrication operations on said articles, such as, but not limited to,in-mold decoration, baking in a paint oven, over-molding, co-extrusion,multilayer extrusion, surface etching, lamination, and/or thermoforming.

Novel aspects of the invention encompass processes for makingcompositions of the invention wherein in some embodiments ammoniumpolyphosphate and cellulosic material are included in the compositionsin such a manner so as to minimize the contact time between ammoniumpolyphosphate and cellulosic material. Illustrative examples forminimizing said contact time include but are not limited toprecompounding all or at least a portion of resinous components andcellulosic material before inclusion of ammonium polyphosphate. In otherembodiments compositions of the invention are prepared in an extrusionprocess, and all or at least a portion of ammonium polyphosphate is fedto the extruder at a down-stream feed-port of the extruder wherein allor at least a portion of alkenyl aromatic resin and cellulosic materialhave been fed at the extruder feed-throat. Any compounding process forcompositions of the invention, including but not limited to down-streamfeeding of ammonium polyphosphate during extrusion, may be performed byfeeding solid ammonium polyphosphate or by injecting a liquid mixture ofammonium polyphosphate optionally in combination with one or moreadditional blend components, for example, at least one adjunct flameretardant such as a liquid adjunct flame retardant. Optionally, anyextrusion process may include vacuum venting at one or more appropriatepoints in the extruder. A particular embodiment of the invention is anextrusion process for preparing a resinous, flame-retardant compositioncomprising (i) 40-66 wt. % ABS, (ii) 9-33 wt. % ammonium polyphosphateand (iii) 14-40 wt. % cellulosic material, wherein ammoniumpolyphosphate and cellulosic material are present in a weight % ratio ina range of 1:2 to 2:1 effective to provide molded articles exhibiting atleast V-1 flame rating as determined according to the UL-94 protocol,and wherein the composition comprises 15-30 wt. % rubber derived fromABS, the rubber content being based on the weight of the entirecomposition, which process comprises the step of adding all or a portionof the ammonium polyphosphate to the extruder down-stream from the ABSand the cellulosic material. In other embodiments of the invention allor at least a portion of alkenyl aromatic resin may be precompoundedwith all or at least a portion of cellulosic material before combinationwith ammonium polyphosphate. Such precompounding may be performed usingknown methods, such as but not limited to extrusion or kneading.

The compositions of the present invention can be formed into usefularticles. Useful articles comprise those which are commonly used inapplications requiring flame resistance and particularly in applicationsrequiring halogen-free (eco-friendly) compositions for flame resistance.In some embodiments the articles comprise unitary articles comprising acomposition of the invention. In other embodiments articles compriseelectrical housings, business machine internal and external parts,printers, computer housings, switches, profiles, window profiles andlike articles. Multilayer articles comprising at least one layer derivedfrom a composition of the invention are also contemplated. Articles, forexample molded articles, made from the compositions of the presentinvention often exhibit V-1 flame rating or better (for example, V-1 orV-0 rating) as determined according to the UL-94 protocol.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present invention to itsfullest extent. The following examples are included to provideadditional guidance to those skilled in the art in practicing theclaimed invention. The examples provided are merely representative ofthe work that contributes to the teaching of the present application.Accordingly, these examples are not intended to limit the invention, asdefined in the appended claims, in any manner.

In the following examples (abbreviated “Ex.”) and comparative examples(“C.Ex.”) the amounts of components are expressed in wt. % unless noted.ABS in the following compositions comprised about 14-17% polybutadienerubber and was obtained from SABIC Innovative Plastics™. High rubber ABS(abbreviated “HR-ABS”) was BLENDEX® 338 comprising about 60-78%polybutadiene rubber and was obtained from SABIC Innovative Plastics™.High impact polystyrene (HIPS comprised less than about 10% rubbercontent. Styrene-acrylonitrile copolymer (SAN) comprised structuralunits derived from about 3:1 styrene:acrylonitrile. Ammoniumpolyphosphate (abbreviated “APP”) was EXOLIT® AP 423 ammoniumpolyphosphate containing about 31-32 weight % phosphorus and wasobtained from Clariant. Cellulose fiber was CreaTech TC180 obtained fromCreaFill Fibers Corp., Chestertown, Md. Wood flour was obtained fromAmerican Wood Flour Company, Schoefield, Wis. Flame retardant propertieswere determined according to the UL-94 protocol. The notation “NC” forflame retardant rating indicates no flame retardancy was observed.Notched Izod impact strength (NII) values in units of joules per meterwere determined according to ISO 180 at room temperature. Flexuralstrength values in units of megapascals and flexural modulus values inunits of gigapascals were determined according to ISO 178.

COMPARATIVE EXAMPLES 1-8 AND EXAMPLES 1-6

Compositions comprising ABS in Table 1 were compounded in an extruderunless otherwise described. The compounded material was molded into testparts and the parts were tested for physical properties. The testresults are shown in Table 1.

TABLE 1 Ex. or C. Ex. C. Ex. Ex. Ex. Ex. Ex. Ex. Ex. C. Ex. Component1^(a) C. Ex. 2^(a) C. Ex. 3^(a) C. Ex. 4 C. Ex. 5 C. Ex. 6 C. Ex. 71^(b) 2^(b) 3^(b) 4^(b) 5^(d) 6^(b) 8^(c) ABS 80 70 60 80 70 60 70 50 5550 55 63 57.7 57.5 Cellulose 20 30 40 — — — — 30 25 20 15 20 30 30 fiberWood flour — — — 20 30 40 — — — — — — — — APP — — — — — — 30 20 20 30 3017 12.5 12.5 FR rating NC NC NC NC NC NC NC V-0 V-1 V-0 V-1 V-1 V-0 NCStrength, — — — — — — — — — — — 62.6 58.2 58.2 MPa Modulus, — — — — — —— — — — — 3.40 3.08 3.06 GPa ^(a)Prepared in an internal mixer ^(b)APPfed downstream of other blend components ^(c)APP fed in extruderfeed-throat with other blend components ^(d)ABS and celluloseprecompounded before blending with APP

Comparative examples 1-3 show that cellulose fiber alone does not impartflame retardant properties to ABS. Comparative examples 4-6 show thatwood flour alone does not impart flame retardant properties to ABS.Comparative example 7 shows that a high level (30 wt. %) of ammoniumpolyphosphate alone does not impart flame retardant properties to ABS.Surprisingly, examples 1-5 show that the combination of cellulosicmaterial and ammonium polyphosphate imparts good flame resistance to ABScompositions either when ammonium polyphosphate is fed down-stream ofthe feed throat while ABS and cellulosic material are fed directly tothe feed-throat of the extruder (example 1-4 and 6) or when ABS andcellulose are precompounded before blending with APP (example 5).Comparative example 8 shows that the combination of cellulose fiber andammonium polyphosphate does not impart good flame resistance to ABScompositions when all three components are fed directly to thefeed-throat of the extruder. Although the invention is in no way limitedby any theory of operation, it is believed that feeding ammoniumpolyphosphate in the feed-throat along with cellulosic material leads todetrimental reaction between these two components. For example, it isbelieved that ammonium polyphosphate can promote cross-linking of atleast some cellulosic material leading to poor dispersion of suchmaterial in a resinous matrix.

COMPARATIVE EXAMPLES 9-21 AND EXAMPLES 7-8

Compositions comprising ABS in Table 2 were prepared with a total rubberconcentration of about 15 wt. %. The rubber level was achieved bycombining two ABS grades with different rubber contents. Thecompositions were compounded in an extruder with downstream feeding ofAPP. The compounded material was molded into test parts and the partswere tested for physical properties. The test results are shown in Table2. Example 7 and example 8 had similar amounts and ratio of ammoniumpolyphosphate and cellulosic material, but in addition example 8 had 10wt. % adjunct flame retardant triphenyl phosphate. The data show thatthe addition of an adjunct flame retardant provided good flameresistance. The addition of adjunct flame retardant also provided moldedparts with better color, better flow properties and allowed the use oflower processing temperature for the composition.

TABLE 2 Ex. or C. Ex. C. C. C. Ex. C. Ex. C. Ex. C. Ex. C. Ex. C. Ex. C.Ex. C. Ex. C. Ex. C. Ex. C. Ex. Component Ex. 9 Ex. 10 11 12 13 14 15 1617 18 19 20 21 Ex. 7 Ex. 8 ABS 87.3 74.6 73.3 72.0 71.4 70.1 68.2 63.763.7 59.3 57.4 55.4 54.2 52.9 40.2 HR-ABS 2.7 5.4 5.7 6.0 6.1 6.4 6.88.0 7.8 8.7 9.1 9.6 9.8 10.1 12.8 cellulose 5 5 5 5 12.5 12.5 20 12.512.5 5 12.5 20 20 20 20 APP 5 5 11 17 5 11 5 11 11 17 11 5 11 17 17 TPP— 10 5 — 5 — — 5 5 10 10 10 5 — 10 FR rating NC NC NC NC NC NC NC NC NCNC NC NC NC NC V-0 Strength, 61.6 50.2 53.7 52.4 60.0 59.3 62.0 57.455.9 41.4 47.9 51.4 55.6 51.9 45.4 MPa Modulus, 2.30 2.31 2.23 2.21 2.682.62 2.74 2.65 2.63 2.29 2.77 2.99 2.98 2.87 3.29 GPa NII, J/m⁻¹ 43 3227 32 27 32 32 27 27 21 21 21 21 21 27

COMPARATIVE EXAMPLES 22-23 AND EXAMPLES 9-12

Compositions comprising ABS in Table 3 were compounded in an internalmixer. The compounded material was molded into test parts and the partswere tested for flame resistance. The test results are shown in Table 3.

TABLE 3 Ex. or C. Ex. Component Ex. 9 Ex. 10 Ex. 11 Ex. 12 C. Ex. 22 C.Ex. 23 ABS 65 60 60 57.5 65 60 cellulose 20 20 20 30 20 20 APP 15 20 1012.5 — — TPP — — 10 — 15 20 FR rating V-1 V-1 V-1 V-0 NC NC

Compositions comprising alkenyl aromatic resin, cellulosic material andammonium polyphosphate in examples 9-12 show good flame resistance. Incontrast, the comparative examples 22-23 which contain ratios ofstyrenic polymer to cellulosic material similar to those ratios inexamples of the invention but which also contain only organophosphorusflame retardant and no ammonium polyphosphate exhibit poor flameresistance.

COMPARATIVE EXAMPLES 24-26 AND EXAMPLES 13-18

Compositions comprising high impact polystyrene (HIPS) were compoundedin an internal mixer. The compounded material was molded into test partsand the parts were tested for flame resistance. Blend compositions andtest results are shown in Table 4.

TABLE 4 Ex. or C. Ex. C. C. C. Com- Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex.ponent 24 25 26 13 Ex. 14 15 16 17 18 HIPS 70.5 66.5 68 65 65.5 63 58 6358 cellulose 12.5 12.5 15 15 12.5 15 15 20 20 APP 17 11 17 15 17 17 1717 17 TPP — 10 — 5 5 5 10 — 5 FR rating NC NC NC NC V-1 V-1 V-0 V-0 V-0

COMPARATIVE EXAMPLES 27-30 AND EXAMPLES 19-26

Compositions comprising polystyrene (PS) were compounded in an internalmixer. The compounded material was molded into test parts and the partswere tested for flame resistance. Blend compositions and test resultsare shown in Table 5.

TABLE 5 Ex. or C. Ex. C. Ex. C. Ex. C. Ex. C. Ex. Ex. Ex. Ex. Ex. Ex.Ex. Ex. Ex. Component 27 28 29 30 19 20 21 22 23 24 25 26 PS 70.5 65.566.5 68 63 65 58 63 58 60 58 56 cellulose 12.5 12.5 12.5 15 15 15 15 2020 25 25 25 APP 17 17 11 17 17 15 17 17 17 15 17 19 TPP — 5 10 —  5  510 —  5 — — — FR rating NC NC NC NC NC NC V-0 V-1 V-0 V-1 V-0 V-0

COMPARATIVE EXAMPLES 31-34 AND EXAMPLES 27-34

Compositions comprising SAN were compounded in an internal mixer. Thecompounded material was molded into test parts and the parts were testedfor flame resistance. Blend compositions and test results are shown inTable 6.

TABLE 6 Ex. or C. Ex. C. Ex. C. Ex. C. Ex. C. Ex. Ex. Ex. Ex. Ex. Ex.Ex. Ex. Ex. Component 31 32 33 34 27 28 29 30 31 32 33 34 SAN 70.5 65.566.5 68 63 65 58 63 58 60 58 56 cellulose 12.5 12.5 12.5 15 15 15 15 2020 25 25 25 APP 17 17 11 17 17 15 17 17 17 15 17 19 TPP — 5 10 —  5  510 —  5 — — — FR rating NC NC NC NC NC NC V-0 NC V-0 V-1 V-1 V-0

While the invention has been illustrated and described in typicalembodiments, it is not intended to be limited to the details shown,since various modifications and substitutions can be made withoutdeparting in any way from the spirit of the present invention. As such,further modifications and equivalents of the invention herein disclosedmay occur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the spirit and scope of the invention as defined by thefollowing claims. All Patents and published articles cited herein areincorporated herein by reference.

1. A resinous, flame-retardant composition comprising (i) 40-66 wt. %alkenyl aromatic resin, (ii) 9-33 wt. % ammonium polyphosphate and (iii)14-40 wt. % cellulosic material, wherein all weights are based on thetotal weight of the composition, wherein the type of ammoniumpolyphosphate is crystal phase II and wherein the ammonium polyphosphateand the cellulosic material are present in a weight % ratio effective toprovide molded articles exhibiting at least V-1 flame rating asdetermined according to the UL-94 protocol.
 2. The composition of claim1, wherein the ammonium polyphosphate and the cellulosic material arepresent in a weight % ratio in a range of 1:3 to 3:1.
 3. The compositionof claim 1, wherein the ammonium polyphosphate and the cellulosicmaterial are present in a weight % ratio in a range of 1:2 to 2:1. 4.The composition of claim 1, wherein the alkenyl aromatic resin isselected from the group consisting of polystyrene,acrylonitrile-butadiene-styrene copolymer (ABS), high-impact polystyrene(HIPS), styrene-acrylonitrile copolymer (SAN),alpha-methylstyrene/acrylonitrile copolymer,alpha-methylstyrene/styrene/acrylonitrile copolymer and mixturesthereof.
 5. The composition of claim 4, wherein the alkenyl aromaticresin is selected from ABS or HIPS and wherein the composition comprises5-50 wt. %, based on the weight of the entire composition, of rubberderived from the ABS or HIPS.
 6. The composition of claim 5, comprising5-35 wt. % rubber derived from the ABS or HIPS and based on the weightof the entire composition.
 7. The composition of claim 1, wherein thecellulosic material comprises or is derived from cellulosic fiber, woodfiber, seed husks, ground rice hulls, newspaper, kenaf, coconut shell,sawdust, alfalfa, wheat pulp, wood chips, wood particles, ground wood,wood flour, wood flakes, wood veneers, wood laminates, paper, cardboard,straw, cotton, peanut shells, bagass, plant fibers, bamboo fiber, orpalm fiber.
 8. The composition of claim 1, which further comprises atleast one adjunct flame retardant.
 9. The composition of claim 8,wherein the adjunct flame retardant is selected from the groupconsisting of monophosphate esters, triaryl phosphates, triphenylphosphate, tricresyl phosphate, tritolyl phosphate, diphenylcresylphosphate, phenyl bisdodecyl phosphate, ethyl diphenyl phosphate,diphosphate esters, aryl diphosphates, resorcinol diphosphate, bisphenolA diphosphate, diphenyl hydrogen phosphate, 2-ethylhexyl hydrogenphosphate and oligomeric phosphates.
 10. The composition of claim 1,which is prepared by an extrusion process wherein at least a portion ofthe ammonium polyphosphate is fed down-stream from the alkenyl aromaticresin and the cellulosic material.
 11. The composition of claim 1, whichis prepared by an extrusion process wherein at least a portion of thealkenyl aromatic resin and the cellulosic material are precompoundedtogether before combination with the ammonium polyphosphate.
 12. Anarticle comprising the composition of claim
 1. 13. An article comprisingthe composition of claim
 8. 14. The article of claim 12, which comprisesan electrical housing, a business machine internal or external part, aprinter housing, a computer housing, a switch, a profile or a windowprofile.
 15. A resinous, flame-retardant composition comprising (i)40-66 wt. % alkenyl aromatic resin, (ii) 9-33 wt. % ammoniumpolyphosphate and (iii) 14-40wt. % cellulosic material, wherein the typeof ammonium polyphosphate is crystal phase II, and wherein the ammoniumpolyphosphate and the cellulosic material are present in a weight %ratio in a range of 1:2 to 2:1 effective to provide molded articlesexhibiting at least V-1 flame rating as determined according to theUL-94 protocol, and wherein the composition is prepared by an extrusionprocess wherein all or a portion of the ammonium polyphosphate is fed tothe extruder down-stream from the alkenyl aromatic resin and thecellulosic material.
 16. The composition of claim 15, further comprisingat least one adjunct flame retardant selected from the group consistingof monophosphate esters, triaryl phosphates, triphenyl phosphate,tricresyl phosphate, tritolyl phosphate, diphenylcresyl phosphate,phenyl bisdodecyl phosphate, ethyl diphenyl phosphate, diphosphateesters, aryl diphosphates, resorcinol diphosphate, bisphenol Adiphosphate, diphenyl hydrogen phosphate, 2-ethylhexyl hydrogenphosphate and oligomeric phosphates.
 17. An extrusion process forpreparing a resinous, flame-retardant composition comprising (i) 40-66wt. % alkenyl aromatic resin, (ii) 9-33 wt. % ammonium polyphosphate and(iii) 14-40 wt. % cellulosic material, wherein the ammoniumpolyphosphate and the cellulosic material are present in a weight %ratio in a range of 1:2 to 2:1 effective to provide molded articlesexhibiting at least V-1 flame rating as determined according to theUL-94 protocol, which process comprises the step of adding at least aportion of the ammonium polyphosphate to the extruder down-stream fromthe ABS and the cellulosic material.
 18. The extrusion process of claim17, wherein the composition further comprises at least one adjunct flameretardant selected from the group consisting of monophosphate esters,triaryl phosphates, triphenyl phosphate, tricresyl phosphate, tritolylphosphate, diphenylcresyl phosphate, phenyl bisdodecyl phosphate, ethyldiphenyl phosphate, diphosphate esters, aryl diphosphates, resorcinoldiphosphate, bisphenol A diphosphate, diphenyl hydrogen phosphate,2-ethylhexyl hydrogen phosphate and oligomeric phosphates.
 19. Anarticle comprising the composition prepared by the process of claim 18.